Conventionally, there has been a refrigerating apparatus disposed with a vapor compression-type refrigerant circuit including a heat exchanger configured such that refrigerant flows in from below and flows out from above as an evaporator of the refrigerant (e.g., see Japanese Patent Application Publication No. S63-204074). In order to prevent refrigerating machine oil from accumulating inside the evaporator, the refrigerating apparatus is configured to extract, from the vicinity of the surface of the refrigerant, the refrigerating machine oil accumulating in a state where it floats on the surface of the refrigerant as a result of the refrigerating machine oil and the refrigerant separating into two layers because the specific gravity of the refrigerating machine oil is smaller than that of the refrigerant, and to return the refrigerating machine oil to the intake side of the compressor.
Further, as an example of a refrigerating apparatus disposed with a vapor compression-type refrigerant circuit, there is an air conditioner disposed with a vapor compression-type refrigerant circuit including: a heat source refrigerant circuit including plural heat source heat exchangers; and plural utilization refrigerant circuits connected to the heat source refrigerant circuit (e.g., see Japanese Patent Application Publication No. H03-260561). In this air conditioner, heat source expansion valves are disposed so that the flow rate of the refrigerant flowing into the heat source heat exchangers can be regulated. Additionally, in this air conditioner, when the heat source heat exchangers are caused to function as evaporators during a heating operation or during a simultaneous cooling and heating operation, for example, control is conducted to reduce the evaporating ability by reducing the openings of the heat source expansion valves as the overall air conditioning load of the plural utilization refrigerant circuits becomes smaller. Moreover, when the overall air conditioning load of the plural utilization refrigerant circuits becomes extremely small, control is conducted to reduce the evaporating ability by closing some of the plural heat source expansion valves to reduce the number of heat source heat exchangers functioning as evaporators or to reduce the evaporating ability by causing some of the plural heat source heat exchangers to function as condensers to offset the evaporating ability of the heat source heat exchangers functioning as evaporators.
Further, in the aforementioned air conditioner, when the heat source heat exchangers are caused to function as condensers during a cooling operation or during the simultaneous cooling and heating operation, control is conducted to reduce the condensing ability by increasing the amount of liquid refrigerant accumulating inside the heat source heat exchangers and reducing the substantial heat transfer area by reducing the openings of the heat source expansion valves connected to the heat source heat exchangers as the overall air conditioning load of the plural utilization refrigerant circuits becomes smaller. However, when control is conducted to reduce the openings of the heat source expansion valves, there is the problem that there is a tendency for the refrigerant pressure downstream of the heat source expansion valves (specifically, between the heat source expansion valves and the plural utilization refrigerant circuits) to drop and become unstable, and control to reduce the condensing ability of the heat source refrigerant circuit cannot be stably conducted. In order to counter this problem, control has been proposed to raise the refrigerant pressure downstream of the heat source expansion valves by disposing a pressurizing circuit that causes high-pressure gas refrigerant compressed by the compressor to merge with refrigerant whose pressure has been reduced in the heat source expansion valves and is sent to the utilization refrigerant circuits (e.g., see Japanese Patent Application Publication No. H03-129259).